Webster, 23, joins the Red Sox for his fourth stint with the big league club this season. For Pawtucket this year, he went 8-4 with a 3.60 ERA (42 ER/105.0 IP), and 116 strikeouts in 21 starts. Over his final eight starts of the regular season, he went 3-1 with a 2.56 ERA (13 ER/45.2 IP) and 49 strikeouts. Webster has made one relief appearance for the PawSox in their International League Semifinals series against Rochester, throwing 1.0 scoreless inning with one strikeout in Game 1 on September 4.

One of six Red Sox pitchers to make his major league debut for the club this season, Webster has gone 1-2 with a 9.57 ERA (28 ER/26.1 IP) in six starts for Boston. He made his debut on April 21 against Kansas City, and earned his first win on July 4 against San Diego.

With today's transaction, Boston's active major league roster is now at 32 players.